How George W. Bush can make the most of the rest of his life.

Herbert Hoover was once asked what, exactly, ex-presidents do with their time. "Madam," he said, "we spend our days taking pills and dedicating libraries."

Hoover was in on the joke. After leaving office under a cloud in 1933, * he spent years mulling his failures. But eventually, President Harry S. Truman asked him to oversee several government projects, from tackling starvation in postwar Europe to making federal agencies more efficient (some projects, alas, remain ongoing). By the time of his death in 1964, Hoover was more popular than when he was in 1933. His secret for overcoming his critics: "I outlived the bastards," he said.

Indeed, many presidents have been better ex-presidents than they were presidents. The ineffectual John Quincy Adams went on to become a respected member of the U.S. House from Massachusetts for nine terms. Martin Van Buren, an unremarkable head of state, became one of the strongest advocates of abolition. After one embattled presidential term, William Howard Taft fulfilled his lifelong dream to become chief justice of the Supreme Court. Which raises the question: How can George W. Bush be the best ex-president he can be?

So far, Bush has only hinted at his plans. After moving to Dallas, he'll work on setting up and funding the George W. Bush Presidential Library. There, he plans to write his take on the major events of his presidency. (Expect a book.) The lecture circuit is no doubt part of the plan. And if his post-presidency is anything like his presidency, the entire country will be clear of brush by 2012.

But the broad strokes of Bush's post-presidency are still unclear.

There are generally two models for the modern ex-POTUS: The fade into relative obscurity favored by Gerald Ford and Ronald Reagan; and the activist, globe-trotting, elder statesman model as practiced by Jimmy Carter and Bill Clinton. (George H.W. Bush has been mostly the former type, though more recently he's teamed with his successor, Clinton, to help victims of the 2004 tsunami in Indonesia and Hurricane Katrina in New Orleans.) For years, the former model was dominant. Of the 34 men who have survived to see their post-presidencies, only a handful of them were young and healthy enough to have a full second act. And even then, remaining in the public eye isn't always an attractive option. Truman, unpopular at the end of his presidency, spent much of his time cultivating his library. Ford continued to suffer from his decision to pardon Nixon after Watergate.

Carter redefined the post-presidency in a way that raises the bar for future exes. Like Truman, he left the White House with punishing poll numbers. Compared with his successor, Reagan, he was seen as a nonentity. But instead of immersing himself in the usual business of legacy-burnishing via a presidential library, he started the Carter Center, an organization dedicated to humanitarian fundraising, research, and conflict resolution. Carter, meanwhile, inserted himself into various global conflicts, chatting up Habitat for Humanity, supervising elections in Nicaragua in 1989, and brokering a peace agreement on President Clinton's behalf in Haiti. For all his globe-trotting do-gooding, he was awarded the Nobel Peace Prize in 2002.

His meddling hasn't always been welcome—Clinton blew up at him for media grandstanding after the Haiti agreement, and Carter's comparison of the Israeli occupation to apartheid has irked some former fans. (His role in the 2008 Democratic National Convention was limited to a comically brief wave.) But he proved that one's post-presidency can outshine—and, in retrospect, redefine—one's presidency.

Bill Clinton followed Carter into humanitarian advocacy, only with a focus on the private sector. Despite some slips during his wife's 2008 campaign, Clinton remains popular. With the attention and influence of a head of state but none of the responsibility, he gives the impression that the only job better than president is former president.

Bush could go either way. On the one hand, he values his personal life. On the other, he's young and has a strong sense of mission. Bush recently described himself as "a Type A personality. I just can't envision myself, you know, the big straw hat and Hawaiian shirt sitting on some beach." He has made noises about wanting to promote freedom and spread democracy.